Multimedia data, whether audio, video, or both, is commonly transmitted as “streaming” media, such that an end user device can begin decoding the multimedia data as the data is downloaded and thus begin the presentation of an audio and/or video program to the device's user without waiting for a transfer of the complete program. As with other media delivery techniques, content providers are very concerned with the application of appropriate digital rights management (DRM) to streaming media, for protecting against unauthorized use of the multimedia data.
Conventional solutions to the protection of multimedia streams, whether the streams are unicast (i.e., transmitted to a single user), multicast (i.e., transmitted to two or more specifically targeted users), or broadcast, typically involve encryption of the streamed media, and may also include a secure key provisioning solution. The keys used for the encryption and authentication may remain the same for a complete session, or they can be refreshed regularly during the session. Some solutions also implement a key hierarchy, with long-term and short-term keys.
The stream decryption and key management required in these systems present a computational burden to the end systems. This may be particularly problematic in portable devices, where available computing power is limited, and/or in circumstances where several media streams are processed simultaneously.